Azer KoÃ§ulu has created an open source tool, Rainbow 9, that simplifies developing web interfaces. It provides an environment to execute and test Javascript, CSS and HTML; sharing and publishing the application.

This is actually very much like google mashup editor which was released recently. Of course, it doesn’t have special tag markup for maps, et.c., but the main similarities is that it’s mainly text-based with a good, usable code editor and possibly more “liveness” than google :)

It seems that quite a lot of people are working on in-browser IDE’s at the moment, with many choosing to focus on the source code /js/html/css, and others focusing almost entirely on WYSIWYG form generation.

It would be interesting to see what would happen if you managed to wed those two worlds, and maybe reuse other peoples components that could have, but wasn’t required to be visible, and then string them along :)